The invention relates to an arrangement and a process for piecing at a spinning unit that is used for producing feed spools consisting of multiple-wound, prestrengthened slivers for a subsequent twisting process or the like. The spinning unit contains two drafting or drawing roller units that each supply one sliver to a device for false-twisting. Following are a device for withdrawing the false twisted slivers as well as apparatus for the joint winding-up of the slivers, which slivers were prestrengthened by means of the false-twisting, onto a feed spool.
In the case of a known spinning unit of the initially mentioned type (European Patent Application EP-A No. 126 659), the two slivers are drawn in the drafting or drawing roller devices to the desired yarn count and subsequently pass through a false-twisting device. From the false-twisting device, they are withdrawn by means of a withdrawing device and are then wound up. Although the false twist that was introduced in the false-twisting device opens up again after the passage is completed, a certain strengthening remains, particularly a winding of the ends of the outer fibers around the sliver core. The two prestrengthened slivers are wound up jointly and in a multiple shape. The resulting spool is used as the feed spool for a twisting that is carried out in a next work step. During the piecing, that is not disclosed in detail, a filament yarn is added to the two slivers as an auxiliary yarn for the purpose of strengthening, which filament yarn is fed in the area of the pair of delivery rollers of the drawing roller devices. The auxiliary yarn, together with the slivers, moves through the false-twisting device and the withdrawal device until it is sucked off. Subsequently, the two filament yarns are cut, after which the slivers that no longer contain any filament yarn are wound onto a spool.
An objective of the invention is to provide a process for piecing that can be carried out in a simple and fast way and is also suitable for automation.
This objective is achieved according to the invention by providing that first the supply of the drafting roller devices is started, after which the slivers are sucked into the pneumatic false-twisting devices and are guided through them and are then gripped jointly, at the outlet of the false-twisting devices, and are placed in a withdrawal device and are fed to a winding-up device.
In the case of the process according to the invention, the adding of auxiliary yarn for the strengthening of the slivers is superfluous so that the expenditures are less than with the above-noted system. In addition, this piecing process can be carried out relatively rapidly, since the two slivers, after passing through the pneumatic false-twisting device, are gripped and processed jointly. This leads to no significantly increased stress for the slivers compared to the normal spinning process, particularly because the supply of the slivers is switched on in time. In this case, it is contemplated in preferred embodiments to place the slivers jointly first in the withdrawal device and then lead them to the winding-up device, or to feed them first to the winding-up device and subsequently insert them in the withdrawal device.
According to certain preferred embodiments of the invention, it is provided that the slivers are first sucked off by means of suction devices that are connected behind the drafting roller devices, before they are taken over by the false-twisting devices and are sucked into them. By means of this intermediate step, it can be ensured that the two slivers move correctly through the drafting roller devices so that the danger of obstructions or the like of the pneumatic false-twisting devices is reduced. In an advantageous development, it is provided that the suction devices, before or during the starting of the sliver supply of the drafting roller devices, are brought into the area of the pairs of delivery rollers of the drafting roller devices and are subsequently moved out of this area, in which case the pneumatic false-twisting devices follow into the area of the pairs of delivery rollers and then take over the slivers. In this way, a clean transfer of the slivers delivered by the drafting roller devices to the pneumatic false-twisting devices can be carried out that is also particularly suitable for an automatic operation.
In a further development of certain preferred embodiments of the invention, it is provided that at the outlet of the false-twisting devices, a suction gripper is connected that receives both slivers, inserts the slivers jointly into the withdrawal device and guides them to the winding-up device. This type of suction gripper has the advantage that it securely receives the slivers that must be received simultaneously and holds them under tension without requiring special measures for the adaptation to the delivery speed of the slivers. This is also advantageous for the conveying of the slivers for the purpose of inserting them into the withdrawal device and, as required, into other devices and for the transfer to the winding-up device, because in this case it is also not necessary to adapt the gripping movement precisely to the delivery speed of the slivers.
In a further development of preferred embodiments of the invention, it is provided that for each piecing operation, an empty spool shell is inserted into the winding up device to which the slivers are transferred that are fed jointly during the piecing. This development of the invention is based on the fact that the frequency of sliver breakage is very low so that the piecing must essentially only be carried out when the feed spool is full onto which the two slivers are wound, and/or the sliver supply from which the slivers are withdrawn is used up.
In a further development of preferred embodiments of the invention, it is provided that the slivers that, at the time of the piecing, are taken over jointly at the outlet of the false-twisting devices, before a renewed winding-up, are connected with sliver ends withdrawn from the produced feed spool. Splicing is particularly suitable for the connection.
In a further development of preferred embodiments of the invention, it is provided that in the area behind the false-twisting devices, the presence of the sliver is monitored and that, in the case of a breakage of one or both slivers, the supply of both slivers is interrupted. In a further development of the invention, it is provided that the slivers are monitored before they enter into the drafting roller devices, and that, when one sliver is absent, the further supply of the drafting roller devices is interrupted. In this way, it is securely prevented that it is not noticed that only one sliver is wound onto the spool.
In a further development of preferred embodiments of the invention, it is provided that, when the sliver supply is interrupted, the pneumatic false-twisting devices are moved out of the area of the pairs of delivery rollers of the drafting roller devices and suction devices are moved into this area. This measure, similarly to the interruption of the supply of the slivers, can be controlled via yarn guards.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.